You need to create a footer or edit the footer.htm file in your photopost directory. Once you have entered the html code the way you want you need to login and go to your admin control panel for photopost. Hit options and then enter where is asks for the path to footer file the server path to that footer

example

/usr/local/apache/htdocs/gallery/footer.htm

clue here you can take the photopost data path and copy and paste it in the footer box just remove data and replace with footer.htm if you dont know what the server path is to the footer.htm file